| 摘要 |
PURPOSE:To easily realize the correct shape and to improve the dimensional stability by a method wherein the spacer concerned is made of polyacetal resin and consists of a cylindrical frame body and lip is provided onto the inner surface of the frame body in the peripheral direction over the whole periphery or a part of the periphery. CONSTITUTION:The spacer concerned consists of a cylindrical frame body 1 and a lip 2, which is provided along the whole periphery of the inner surface of the cylindrical frame body 1. The top and under surfaces of the lip 2 of a positioning spacer is preferably planes. The projected part 5 of the lip 4 is provided for positioning by being brought into linear contact with the concave spherical surface of a mold. Polyacetal resin is an engineering plastic used as substitution for metal and consists of formaldehyde polymer or copolymer and has high strength and rigidity, good dimensional stability, excellent fatigue characteristics and high wear resistance and consequently is the most excellent material for positioning spacer. |
